Antimuta Genicity of Hom Nil Rice and Black Glutinous Rice Using Somatic Mutation and Recombination Test

Abstract

Raw, cooked and fermented Hom Nil rice (Oryza sativa) and black glutinous rice (Oryza sativa var. glutinosa) were assessed for their mutagenicity and antimutagenicity against in vivo formed nitrosomethylurea in Drosophila melanogaster. In antimutagenic assay, 3-day old, trans-heterozygous (mwh flr⁺/mwh TM3) larvae derived from mating virgin females (Oregon wing flare strain) and males (multiple wing hair stain) were fed on experimental media that contained each rice sample substituted for corn flour and two mutagen precursors, namely methylurea and sodium nitrite and then the mutant wing spots of surviving flies were analyzed. This study found that all samples did not significantly induce the frequencies of mutant spots at any testing amounts to be higher than that of the negative control. This indicated that none of them was mutagenic. All of rice samples exhibited the antimutagenicity against in vivo formed nitrosomethylurea and the fermented black glutinous rice possessed the highest effect. The antimutagenic activity of these pigmented rices might possibly be due to their antioxidative substances including phenolic compounds which might scavenge the free radicals derived from the mutagen during mutagenesis. Therefore, this study suggested that Hom Nil rice and black glutinous rice may be a good choice for health concerning consumers. Further study should be conducted to investigate the active compound(s) and mechanism of antimutagenic activity of these types of pigmented rice.